The present disclosure relates to a method and apparatus for reducing clutch drag loss. More particularly, a clutch having a moveable cover selectively restricting a flow of oil within the clutch is disclosed.
Typical wet clutches include a drum rotatable relative to a hub. A plurality of outer clutch plates are in driving engagement with the drum and a plurality of inner clutch plates are in driving engagement with the hub. The inner and outer clutch plates are interleaved with one another. Some friction plate clutches are designated as wet clutches and have oil positioned between the hub and the drum in contact with the inner and outer clutch plates. Wet clutches are typically operable in a disengaged mode where little to no torque is transferred between the drum and the hub and an engaged mode when torque is transferred between the clutch hub and the clutch drum.
When the known wet clutch is in the disengaged mode, oil may be pumped across the outer plates and the inner plates. Alternatively, oil is trapped between the hub and the drum and remains located between the hub and the drum during all modes of operation. As such, a certain amount of energy is required to shear the oil located between the inner and outer clutch plates when the clutch is in the disengaged mode. This energy may be referred to as clutch drag loss. Clutch drag loss therefore becomes a parasitic energy loss associated with vehicles operating with wet clutches of this design.